Increasing national energy requirements are rapidly depleting the reserves of higher grade carbonaceous fuels used in conventional power production. The use of cruder, high sulfur content fuels will become essential in the near future. Technology has developed for the refinement of such fuels to produce gaseous or liquid products which may be used in conventional power plants without substantial change in design and with minimal effect on the environment.
These refining processes, typified by coal gasification and coal liquification, while effective in producing high quality fuels are costly to install and operate.
One of the problems associated with the combustion of sulfur bearing fuels is the formation of volatile sulfur oxides. Many processes have been devised for suppressing these emissions by either mixing an alkaline carbonate an alkaline earth carbonate, or a mixture thereof with the fuel or scrubbing the stack gases with a slurry of the carbonate. While an effluent gas of acceptable quality can be obtained the methods suffer the disadvantage of requiring the transportation of enormous quantities of the alkaline carbonate or alkaline earth carbonates to the plant location and the disposition of an equal volume of sulfate salt.
Processes have been developed by which free and combined sulfur, such as pyritic, organic or elemental sulfur, in coal are removed to produce a low sulfur coal which can be burned for the production of power without causing air pollution due to sulfur dioxide emission. See U.S. Pat. Nos. 3,824,084 and 3,960,513. These processes involve producing a coal-water slurry which is contacted with air under conditions of heat and pressure. Combustion of the coal does not take place and the low sulfur coal is subsequently isolated. It is apparent that these procedures do not provide a unitary process by which a high sulfur carbonaceous fuel can be oxidized to produce power while concurrently removing the sulfur content thus avoiding adverse effects on the environment.
Processes for the wet oxidation of carbonaceous materials are known particularly for the elimination of waste materials. See U.S. Pat. Nos. 2,665,249 and 2,944,396. These known processes do not, however, provide the necessary technology for wet oxidation of high sulfur containing fuel for the production of usable power while concurrently removing the sulfur and avoiding pollution of the environment.